Wad column device



` Jam.` 17,` 1967 Filed .April 6, 1964 R. W. COMERFORD WAD COLUMN DEVICE 2 Sheets-Sheet l INVENTOR.

RONALD W. COMERFORD ATTORNEY R. W- COMERFORD 2 Sheets-Sheet 2 Fil-ed April 6, 1964 FIG.

INVENTOR.

D R O F R m o n C N w. D 2. T M M N J O ,J R /w, Y B 9 Ll 2 H 9 I liv l ,ll n Q (JO 3 2 9 t United States Patent() 3,298,313 WAI) CULUMN DEVICE Ronald W. Comerford,` 11905 Milan Ave.,

Cleveland, Ohio 44111 Filed Apr. 6, 196,4, Ser. No. 357,495 5 Claims. (Cl. 102---95)` The present invention relates generally to ammunition and relates more particularly to a wad construction for use between a propellant charge and a shot charge ina shotguncartridge case. A

Applicants prior applications, Serial No. 205,047, iiled June 25, 1963, entitled Pouchwad, now abandoned, and Serial No. 232,420, led October 23, 1962, and entitled Shotgun Cartridgefdisclose wad structures which have been characteristically termed pouchwads A pouch wad is an obturating wad and wad column in combination with a pouch for containing and confining a shot charge of pellets or the like. The pouchwads described in the above-identified applicationseach comprises a generally elongated tubular member having a closed end adjacent the propellant charge in the lcartridge case and an open end4 terminating near infolded closure portions of the cartridge case. The closed end of the tubular member forms an obturating wall confronting the propellant charge. A center support structure is disposed within the tubular member and extends from the enclosed obturating wall end toward the shot charge to substantially the height of the desired wad column. Each pouchwad further includes a disc or fiber or other suitable material disposed within the open end of the tubular member and seatingon the center support structure and on portions of the tubular wall to form a retaining shelf for the shot charge.

The Wad column structure of the present pouchwad differs from that disclosed in these prior filed applications in several respects which provide the present pouchwad with advantages not previously available. In the present wad structure, an obturating wall is provided for ocnfronting the propellant charge. A shot retaining wall is spaced longitudinally from 4the obturating wall. Elongated support walls support and maintain the obturating and shot retaining walls in spaced, parallel relation. The `obturating and shot retaining walls and the support walls together make up a wad column portion of the present pouchwad and are integrally formed, as by molding, from a suitable resilient material. Where a complete pouchwad is desired, the tubular pouch wall is also integrally formed with the wad column portion.

Because all of the elements of the present wad structure `are integrally formed at the time of manufacture, there is no need for a separate ber disc to form the shot retaining wall. Elimination of the separate ber support disc eliminates the eXtra time and expense required for the manufacture of the disc separate from the wad structure and also eliminates the necessity of having to assem ble the disc and the wad structure prior to insertion into a cartridge case.

The present wad construction also does not require the portion of the tubular member zbetween the obturating and shot retaining walls. There is no wad column structure between the obturating and shot retaining walls to engage the cartridge case. A The only points of contact or engagement between the wad structure and the cartridge case are at the obturating and shot retaining walls, These latter points of engagement are desirable and necessary to perform the obturating function and to maintain the ICC shot charge ahead of the wad column portion. Elimination of the tubular member thus reduces frictional drag on the wad structure as it is expelled from the cartridge case and from a barrel of-a weapon in which the cartridge is red. Elimination of the tubular member also reduces the amount of materials required to make the wad structure and provides a light weight wad structure which has a low cost of manufacture. The light weight construction of the present wad structure and the large reduction in frictional drag of the wad structure both contribute to providing an absolute minimum of recoil when a cartridge using the present wad structure is fired in a weapon.

Another feature of the present wad structure is the arrangement of the support walls. At least two walls are provided and are arranged substantially at right angles to one another and are connected to one another to reinforce each other as well as reinforcing the obturating and shot retaining walls. Preferably, the support walls intersect one another and form a cross-like structure in cross section. The provision of these transversely arranged, intersecting support walls provides suicient cushioning of the shot charge upon ignition of a propellant charge in a cartridge in which the present wad structure is used and also has sufficient rigidity to withstand excessive compression during loading of the cartridge case so that there is no tendency to spring back after the end of the cartridge case in infolded and crimped to cause that crimp to open.

Accordingly, an object of the present invention is to provide a new and improved wad structure that is integrally formed and completed at the time of manufacture and does not require the manufacture of additional pieces and the later assembly of such additional pieces to complete a wad structure.

Another object of the present invention is to provide an obturating wad structure which has a minimum number of points of engagement with a cartridge case and a barrel interior -of a weapon in which it is used.

Still another object of the present invention is to provide a new and improved wad structure which is light weight and has a low cost of manufacture.

Yet another object of lthe present invention is to provide a new and improved Wad structure which produces a minimum of recoil when used.

A final object of the present invention is to provide a new and improved wad structure which is suciently re* silient to provide cushioning of the shot charge but has suflicient rigidity to withstand excessive compression during loading.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawing in which:

FIGURE l is an enlarged, elevational view in crosssection of a cartridge case employing the wad structure of the present invention :as taken along line 1-1 in FIG- URE 2;

FIGURE 2 is a cross-sectional view of the cartridge case and the present wad structure as taken along line 2 2 in FIGURE l;

FIGURE 3 is a perspective view of the wad structure of the present invention;

FIGURE 4 is a fragmentary, cross-sectional view of a molding apparatus utilized in -a preferred method of making the present wad structure as taken along line 4 4 in FIGURE 5;

FIGURE 5 is an elevational view, partly in cross-sec- 3 tion, of the molding apparatus of FIGURE 4 as taken along line 5-5 in FIGURE 4;

FIGURE 6 is a fragmentary, cross-sectional view taken along line 6 6 in FIGURE 5;

FIGURE 7 is an elevational View, partially in cross-Section, similar to FIGURE 5 and taken at right angles to the position shown in FIGURE 5 as indicated by the line 7-7 in FIGURE 6;

FIGURE 8 is a fragmentary, cross-sectional view similar to FIGURE 4 showing the molding apparatus in a position to eject a wad structure.

FIGURE 9 is an elevational view, partially in crosssection also showing the molding apparatus in a wad ejectment position as in FIGURE 8;

FIGURE 10 is a fragmentary View, partially in crosssection and similar to FIGURE 5, showing an alternate core :piece of the molding apparatus for forming a modified wad structure; and

FIGURE 1l is an elevational view of a wad structure formed by the molding apparatus arrangement of FIG- URE l0.

Referring to the drawings, there is shown in FIGURES 1 3 a composite cartridge generally indicated by the reference character 11 which uses a preferred form of the wad structure of the present invention. The composite cartridge 11 includes a cylindrical cartridge case 13 and a metal base 14. The metal base 14 includes a cylindrical portion 15, a transverse portion 16 enclosing a bottom end of the cylindrical portion 15, and a primer-receiving portion 17 located centrally in the transverse portion 16 and extending longitudinally of the cylindrical portion 15. A circumferential rim 18 is provided at the juncture of A cross-like spacing and supporting structure 40 extends between the obturati-ng wall 33 and the shot retaining wall 34 and maintains the walls 33, 34 in their longitudinally spaced, parallel relation. The spacing and support structure 40 includes a first spacing and supporting wall 41. Transverse spacing and support walls 42, 43 extend from opposite sides of the first support wall 41. The transverse support walls 42, 43 are at right angles to the support wall 41 where they intersect the support wall 41 and form a cross-like structure in cross section as is shown in FIGURE 2. The transverse support walls 42, 43 extend from the support wall 41 to adjacent the outer annular surfaces 37, 38 of the obturatiug and shot retaining walls 33, 34. The support wall 41 and the support walls 42, 43 are centered on perpendicular diameters of circles defined by the annular surfaces 37, 38.

Additional transverse walls 44-47 extend from both sides of the first support wall 41 to the outer annular surfaces. The additional transverse support walls 44-47 are arranged spaced and preferably parallel to the transverse support walls 42, 43. Aligned pairs of support walls 44, 45 and 46, 47 are located on opposite parallel chords of the circles defined by the annular surfaces. The additional transverse support walls 44-47 space and support quadrants of the obturating and support walls 33, 34 lying between the support walls 41-43 and prevent longitudinal deformation and sagging of the obturating the cylindrical and transverse portions 15,V 16 to retain 'I the cartridge in the breech of a particular weapon in use and to provide an edge for ejecting the cartridge after use.

The cylindrical portion 15 of the metal base 14 surrounds the lower, powder charge portion of the cartridge case 13. The rn-etal base 14 reinforces the portion of the cartridge case 13 containing the powder charge and also provides a surface or edge by means of which the cartridge is locked in the breech of the weapon'in use.

A basewad 29 is provided in the base or lower end of and shot retaining walls 33, 34.

The end or outerm-ost surfaces of the support walls 41-47- are `effectively recessed in that they curve inwardly to maintain the support walls 41-47 substantially spaced from'the interior surface of the cartridge oase 13.*1See `fo-rzexample, Icurved end surfaces 48, 49 of the 4suppo'rt'wall l41 [in FIGURE 1. The spacing between thecartr-idge case 1 3 and the support walls 41-47 minimizes frictional Contact and prevents interference with the" "obturating' function of the obturating wa-ll 33.

' Thecurved end surfaces of the `support walls 41-47 the cartridge case 13. A firing channel or flash hole 21 extends axially through the centerof the basewad 20. The flash hole 21 opens into a powder chargereceiving cavity 22 of the basewad 2t. A primer 23 is disposed in the primer receiving portion 17 of the metal base 15 and extends axially into the flash hole 21. or propellant charge 25 is provided in the powder charge cavity 22. The primer 23 ignites the powder charge 25 in the usual manner of a central-fire system.

An integral pouchwad 30 employing the wad structure of the present invention is telescoped within the cartridge case 13 over the top of the powder charge 25. The pouchwad 30 is `made of a suitable resilient material, preferably a synthetic plastic material such as polyethylene The pouchwad 30 includes a wad column portion 31 and a shot receiving pouch or pocket portion 32.

The wad column portion 31 includes a lower obturating wall 33 confronting the powder charge 25 and an upper shot retaining wall 34 longitudinally spaced from the obturating wall 33 land confronting a shot charge 35 of pellets or the like. The obturating and shot retaining walls 33, 34 have outer anuular surfaces 37, 38 respectively, which are sized to snugly engage and closely fit within the interior surfaces of the cartridge case 13. The lower or rearward 'obturating wall 33 includes a rearwardly longitudinally extending tapered skirt portion 36. The tapered skirt 36 is very flexible and expands radially outward upon ignition of the powder charge 25 to provide a seal between the wad column portion 31 and the interior surface of `the cartridge case 13. The seal provided by the tapered skirt 36 prevents the escape, or blow-by, of explosion gases between the wad column portion 31 and the cartridge case 13.

A powder although recessed'extend t0 the annular surface 37, 38 to provide s u'pport across the entire diameter of the obturating and shot retaining walls 33, 34.

The pouchportfion 32 includes a cylindrical wall 5f) extending forwardly from the sh-ot iretaining wall 34 and'terrninatingyat the forward end 51. The cylindrical pouch wall 50 is weakened or preferably split longitudinally in av plurality of locations 52 to permit the shotreceiving pouch to open as it emerges from the muzzle of a barrel in which the cartridge is being used. The splits 52 divide the pouch wall 50 into a plurality of cylindically contoured sections. In the embodiment shown in the drawing, there are four such splits S2 dividing the pouch wall into four cylindrically contoured sections. The opening of the shot-receiving pouch portion 32 may be likened to that of a flower. In other words, as the pouchwad emerges from the confines of a barrel, each cylindrically contoured section of the cylindrical pouch wall 50 Iis blown from tit-s substantially longitudinally extending position confining the shot charge to a somewhat radially extending position releasing the shot charge.

As show n in FIGURES 4-10, the present wad structure is made preferably by an injection molding process utilizing two matin molding pieces 61, 62. The two molding pieces 61, 62 are the end portions of elongated molding pieces having a plurality of molding stati-ons. Since each of the molding stations are substantially identical, only the-molding station at the end of the molding pieces is shown and described. At this molding station, the molding pieces 61, 62 have semi-circular molding half cavity surfaces 63, 64 respectively, and surfaces defining support wall forming projections 65-72 The molding -pieces 61, 62 are movable from between an abutting or molding position shown inl FIGURES 4 7 to a relatively spaced or ejectrnent -position shown in FIGURES 8 and 9. The-molding pieces61, 62 have confronting surfaces 79, 89 which abut when the molding pieces 61, 62 are j ends of the projections 65-72 define a support wall cavity space 83 for form-ing the support wal-l 41. The parallel wall surfaces of the projections 65-72 define transverse wall cavities 84-89 for forming the transverse walls 42- 47.1

The mold pieces 61, 62 are counterbored at the ends of the cylindrical molding cavity to form annular shoul- Vder stopV surfaces` 91, 92. A cylindrical core piece 9.3

is provided and includes a cylindrical shank portion 94 and a cylindrical pouch forming portion 95. A radially extending shoulder `surface 96 connects the surfaces of the shank and pouch forming portions 94, 95. The core piece 93 is movable between a molding position (FIG- URES -7) and a wad ejection position (FIGURE 9).

The radial shoulder surface 96 -on the core piece 93 abuts the` stop surface 91 near the top surfaces of the molding pieces 61, 62 to limit the inward movement of the pouch defining portion 95 into the molding cavity so that an end surface 98 Eof the core piece 93 defines a space 99vabove the top surfaces of the support wall form ing projections 65-72. The space 99 is for forming the shot retaining wall 34 of the pouchward structure 30.

The substantially cylindrical surface of the pouch forming core portion 95 is smaller in diameter than the molding cavity so that its defines la substantially cylindrical space 100 between the core piece 93 and the molding pieces 61, 62. The cylindrical space 100 is for forming 4the cylindrical wall 50 of the wad structure 12. The core piece 93 further includes a plurality of elongated slit forming projections 101 projecting radially from the pouch forming core portion 95 and extending from the radial shoulder 96 to adjacent the circular end surface 98. The slit forming projection 161 project sufficiently to engage the cylindrical interior `surfaces 63, `64 the molding cavity so as toisplit the cylindrical wall forming space 100 into a plurality of fcylindrically contoured segments and in this manner form the slits in the cylindrical pouchwall 50..

An obturating skirt forming core piece 111 is provided and includes a shank portion 112, a cylindrical skirt forming porti-on 113, a radially extending shoulder 114 connecting the surfaces of the shank 'and ski-rt forming portions, and an end surface 115. The obturating skirt forming core piece 111 is movable between a wad molding position (FIGURES 5-7) Iand a wad ejectment position (FIGURE 9). The radially extending shoulder 114 abuts the stop surface 92` to limit thc movement of the skirt forming core pie-ce 111 when the molding position. The end surface 115 in the molding position defines an obturating wall forming cavity space 116 with the lower surfaces of the support -wall forming projections 65-72. The cylindrical skirt forming portion 113 has an outer diameter smaller than the diameter of the cylindrical molding cavity and defines a cylindrical obturating skirt forming cavity space 118 with the internal surfaces 63, 64 of the molding pieces 61, 62.

The molding piece 61 has a plastic wad material injection bore 120 which communicates with the space 85 between the support wall forming projections 66, 67. The molding piece 62 includes a pair of ejection pin bores in which ejection pins 121, 122 are slidably disposed. The ejection pins 121, 122 are movable between a molding position (FIGURE 4) and a wad structure ejectment position (FIGURE `8) where they extend into the spaces 87, 89.

To begin a cycle of operation, a suitable mechanism (not shown) moves the two molding pieces 61, 62 together so that the surfaces 79, are in abutment and the molding pieces 61, `62 are held together in that molding position by a press mechanism of a conventional ejection molding apparatus. Another suitable mechanism (not shown) moves the core pieces 93, into their respective open ends of the cylindrical molding cavity until their radially extending shoulders 96, 114 abut the shoulder stop surfaces 91, 92 on the molding pieces 61, 62. When the molding pieces 61, 62 are in the molding Iposition, the ejection pins 121, 122 are in a withdrawn molding position Where their end surfaces are contiguous with `the interior surface 64 of the molding cavity. The molding pieces 61, 62 and the core pieces 93, 95 are now in their wad molding position and together define a wad cavity which Vtakes theshape ofthe pouchwad shown in FIG- URE 3.

Sufiicient synthetic plastic material in a flowable state is introduced into the wad cavity through the injection bore to fill the molding cavity. As is conventionally known, polyethylene is suitable for injection molding purposes at temperatures of approximately 220 to 320. The plastic material so'lidies, the core pieces 93, 95 are then moved out of the molding cavity to their ejection positions, and the molding pieces 61, 62 are caused to separate. As the molding pieces 61, 62 separate and move to their ejection position, the ejection pins 121, 122 engage the end surfaces of the two outside transverse sup port walls 44, 46 and assure that the finished pouch wad structure 30 is ejected from the molding pieces 61, 62. The molding pieces 61, 62 are suitably modified to assure that the finished pouch wad strcture 30 will be pulled from the molding pieces 61 -by the molding piece 62. For example, the space between the spport wall forming projections 70, 71 may be somewhat dove-tailed in appearance to form a slight interlock between the finished wad 30 and the molding piece 62 to assure 'that the wad will be pulled from the molding piece 61 by the molding piece 62 an dthat the ejection pins 121, 122 will be then necessary to eject the finished wad structure 30` from the molding piece 62. After the finished wad structure 30 drops from within the molding pieces 61, 62, the molding pieces 61, 62 are again moved together to start an other cycle.

As the synthetic plastic material cools, the support walls 41-47 tend to shrink slightly. This slight shrinkage causes their end surfaces .to curve inwardly. See, for example, end surfaces 48, 49 of support wall 41. This inward curving caused by the shrinkage eliminates the necessity of cutting away portions of the support walls 41-47 or otherwise modifying them to recess them relative to the annular Wall surface 37, 38.

A particular advantage of the present method and apparatus for molding the wad structure 30 is versatility for molding several different wad structures having the sidecored effect of the wad column portion 31. These several different wad structures are readily available by modifying the movable core pieces 93, 95 only. For example, a wad column 121 shown in FIGURE ll not having the pouch portion 32 of the `wad structure 30, is easily made with the sarne molding pieces 61, 62 by the arrangement of molding and core pieces shown in FIGURE lO. In the molding apparatus shown in FIGURE 10, a core portion 95 of a core piece 93 fits snugly within the molding cavity and its end surface 98 is spaced from the fop surfaces of the support wall forming projections 65-72 the shot-retaining wall 34 of the wad column 121 without a cylindrical shot receiving pouchwall.

If it is desired to make only wad columns without pouches, then a movable core piece 93' is not required and the `mold pieces 61, 62 can be extended to fill the space occupied by the core piece 93. It `is also possible to eliminate the movable core piece 95 by also forming the molding pieces 61, 6-2 to occupy the space occupied by the core piece 95 in its molding position. In the latter molding arrangement, the resilient nature of t-he plastic material of a finished Wad structure enables the obturating skirt 36 which extends into the ski-rt forming space 118 to distend sufficiently to permit the molding pieces 61, 62 to move apart and eject the wad structure 121. Thus, with the present wad column structure having a side-cored appearance, it is possible to make a complete integral wad column with only two movable molding parts or dies.

A third wad column structure is possible by modifying the end of core piece 93 to also have an obturating skirt forming cylindrical portion similar to the skirt forming cylindrical portion 113 on the core piece 111. In this latter arrangement, a finished wad structure would have an obturating skirt on both ends so that the wad structure may be inserted either end first into a cartridge case over the propellant charge. In the latter combination, it is further possi-ble to make one skirt forming po-rtion longer than the other so that the obturating skirt formed on one end of the wad structure is longer than the o'bturating skirt on the other end so that the wad structure is usable in any one of a variety of cartridge cases having different height basewads and still have the same shot charge capacity within each cartridge case.

The present wad structure, especially as manufactured by the preferred method disclosed, has several distinct advantagesl The present wad structure is extremely light weight and provides a minimum of friction within the `cartridge case and within the barrel of a weapon when in use. The wad column portion of the present wad structure is side-cored in appearance and requires a minimum of materials to provide the necessary spacing and support between the obturating and shot retaining walls. This minimum of materials not only provides a lower cost of manufacture, ybut also produces an extremely light weight wad structure which providesV a minimum of weapon recoil and results in exceptionally quick pouch opening upon emergence of a pouchwad from the barrelto release the shot charge at the earliest possible moment. The present wad column structure having a rst longitudinal support Wall extending laterally between the outer annular surfaces of the obturating and shot retaining walls, and transverse additional walls connected to the first wall and extending laterally from the first wall assures that the obturating and shot retaining Walls will be maintained in their longitudinally spaced relation without any appreciable deformation during tiring of the propellant charge and with suicient cushioning to avoid rearward jamming of the shot charge when the cartridge is tired.` The transverse arrangement of the additional support Wall with its side cored appearance permits a plurality of the present integral wad structures to be economically molded by a minimum of mold parts and a minimum of required mold space. Although the support structure has sufficient resiliency to provide cushioning, it also has sufiicient rigidity so that it is not excessively compressi'ble during loading of the cartridge case and has practically no tendency to spring back after a cartridge case is loaded. Thus, premature uncrimping of the forward end of the cartridge case is thereby avoided.

Although the invention yhas -been described in its preferred `form with a certain degree of particularity, it is understood that the present disclosure of the preferred fonm has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention hereinafter claimed.

What is claimed is:

1. A wad column structure for use between a propellant charge and a shot charge in a cartridge case, said wad structure comprising:

(a) an obturating wall for confronting the propellant charge, said obturating wall having an annular outer 3 surface for engaging interior surfaces of the cartridge case;

(b) a shot retaining wall in spaced, parallel relation to 4said obturating wall for confronting the shot charge, said shot retaining wall having an outer annular surface for engaging interior surfaces of the cartridge case; l

' (c) a support structure extending longitudinally between said obturating and shot retaining walls and maintaining said walls in spaced, parallel relation;

(d) said support structure comprising:

(i) a plurality of thin support walls defining planes extending longitudinally between said obturating and shot retaining walls and laterally intersecting said walls on imagina-ry chords of circles defined Yby the annular surfaces of said obturating and shot retaining walls,

(ii) a first of said support w'alls'extendingV longitudinally ibetween said obturating and shot retaining walls and extending laterally to adjacent the annular surfaces on each end of imaginary chords located by the plane defined -by said rst wall,

(iii) additional support walls extending longitudinally between said obturating and shot retaining walls and transversely of said first wall from each side of said first wall to adjacent the annular surfaces on their respective sides of the rst wall,

(iv) said additional walls being connected to said rst wall; and

(e) said obturating wall, said shot retaining wall, and said support structureA comprising an integrally molded structure.

2. The device 0f claim 1 wherein eacli of said additional support walls on one side of said first support wall aligns with and is paired with one of said additional support' walls on the other `side of said rst support wall, and each such pair of said additional support Walls extends to adjacent said annular surfaces so as to define chords of the circles dened tby' said annular surfaces.

3. The device of claim 1 wherein essentially complete peripheral portions of the entire support structure that extends between the obturating and shot retaining walls are spaced inwardly from the outer annular surfaces of the obturating and shot retaining walls so as to be spaced from the cartridge case when in place therein.

4. The device of claim 1 wherein the support walls have outer edges that are spaced inwardly of an imaginary cylindrical surface extending between the annular outer surfaces of the shot retaining and obturating walls.

5. A wad column structure which may be integrally molded as a single piece structure from a suitable synthetic plastic material, said wad column comprising:

(a) an obturating wall;

(b) a shot retaining' wall disposed parallel to and longitudinally spaced from said obturating wall;

(c) a rst support wall means defining a plane and extending longitudinally between said obturating and shot retaining walls and extending laterally across the obturating and shot retaining walls =to adjacent edge surfaces of the obturating and shot retaining walls; and

(d) a plurality of additional support walls lying in parallel planes extending ybetween said obturating and shot retaining walls and intersecting said first support wall at substantially right angles thereto at spaced locations and extending from both sides of said first support wall so as to define a plurality of cross-like support structures in cross sections at each of said spaced locations.

(References on following page) References Cited bythe Examiner UNITED STATES PATENTS FOREIGN PATENTS 1,107,647 10/ 1955 France. 

1. A WAD COLUMN STRUCTURE FOR USE BETWEEN A PROPELLANT CHARGE AND A SHOT CHARGE IN A CARTRIDGE CASE, SAID WAD STRUCTURE COMPRISING: (A) AN OBTURATING WALL FOR CONFRONTING THE PROPELLANT CHARGE, SAID OBTURATING WALL HAVING AN ANNULAR OUTER SURFACE FOR ENGAGING INTERIOR SURFACES OF THE CARTRIDGE CASE; (B) A SHOT RETAINING WALL IN SPACED, PARALLEL RELATION TO SAID OBTURATING WALL FOR CONFRONTING THE SHOT CHARGE, SAID SHOT RETAINING WALL HAVING AN OUTER ANNULAR SURFACE FOR ENGAGING INTERIOR SURFACES OF THE CARTRIDGE CASE; (C) A SUPPORT STRUCTURE EXTENDING LONGITUDINALLY BETWEEN SAID OBTURATING AND SHOT RETAINING WALLS AND MAINTAINING SAID WALLS IN SPACED, PARALLEL RELATION; (D) SAID SUPPORT STRUCTURE COMPRISING: (I) A PLURALITY OF THIN SUPPORT WALLS DEFINING PLANES EXTENDING LONGITUDINALLY BETWEEN SAID OBTURATING AND SHOT RETAINING WALLS AND LATERALLY INTERSECTING SAID WALLS ON IMAGINARY CHORDS OF CIRCLES DEFINED BY THE ANNULAR SURFACES OF SAID OBTURATING AND SHOT RETAINING WALLS, 